1. Field of the Invention
The present invention relates to an optical recording medium which allows rewriting, and more particularly to a method and apparatus of recording data in the optical recording medium, wherein defect areas can be managed.
2. Description of Related Art
An optical storage medium is generally divided into a read only memory (ROM), a write once read many (WORM) memory into which data can be written one time, and rewritable memories into which data can be written several times. Rewritable optical storage mediums, i.e. optical discs, include rewritable compact discs (CD-RW) and rewritable digital versatile discs (DVD-RW, DVD-RAM, DVD+RW).
The operations of writing and playing back data in a rewritable optical disc may be repeated. This repeated process alters the ratio of storage layers for recording data into the optical disc from the initial ratio. Thus, the optical discs lose its characteristics and generate an error during recording/playback. This degradation is indicated as a defective area at the time of formatting, recording on or playing back from an optical storage medium. Also, defective areas of a rewritable optical disc may be caused by a scratch on its surface, particles of dirt and dust, or errors during manufacture. Therefore, in order to prevent writing into or reading out of the defective area, management of such defective areas is necessary.
FIG. 1 shows a defect management area (DMA) in a lead-in area and a lead-out area of the optical disc to manage a defect area. Particularly, the data area is divided into a plurality of zones for the defect area management, where each zone is further divided into a user area and a spare area. The user area is where data actually written and the spare area is used when a defect occurs in the user area.
There are four DMAs in one disc, e.g. DVD-RAM, two of which exist in the lead-in area and two exist in the lead-out area. Because managing defective areas is important, the same contents are repeatedly recorded in all four DMAs to protect the data. Each DMA comprises two blocks of 32 sectors, where one block comprises 16 sectors. The first block of the DMA, called a DDS/PDL block, includes a disc definition structure (DDS) and a primary defect list (PDL). The second block of the DMA, called an SDL block, includes a secondary defect list (SDL). The PDL corresponds to a primary defect data storage and the SDL corresponds to a secondary defect data storage.
The PDL generally stores entries of defective sectors caused during the manufacture of the disc or identified when formatting a disc, namely initializing and re-initializing a disc. Each entry is composed of an entry type and a sector number corresponding to a defective sector. The SDL lists defective areas in block units, thereby storing entries of defective blocks occurring after formatting or defective blocks which could not be stored in the PDL during the formatting. As shown in FIG. 2, each SDL entry has an area for storing a sector number of the first sector of a block having defective sectors, an area for storing a sector number of the first sector of a block replacing the defective block, and reserved areas.
Also, each SDL entry is assigned a value of 1 bit for forced reassignment marking (FRM). A FRM bit value of 0 indicates that a replacement block is assigned and that the assigned block does not have a defect. A FRM bit value of 1 indicates that a replacement block has not been assigned or that the assigned replacement block has a defect. Thus, to record data in a defective block listed as a SDL entry, a new replacement block must be found to record the data. Accordingly, defective areas, i.e. defective sectors or defective blocks, within the data area are replaced with normal or non-defective sectors or blocks by a slipping replacement algorithm and a linear replacement algorithm.
The slipping replacement is utilized when a defective area or sector is recorded in the PDL. As shown in FIG. 3A, if defective sectors m and n, corresponding to sectors in the user area, are recorded in the PDL, such defective sectors are skipped to the next available sector. By replacing the defective sectors by subsequent sectors, data is written to a normal sector. As a result, the user area into which data is written slips and occupies the spare area in the amount equivalent to the skipped defective sectors.
The linear replacement is utilized when a defective block is recorded in the SDL or when a defective block is found during playback. As shown in FIG. 3B, if defective blocks m and n, corresponding to blocks in either the user or spare area, are recorded on the SDL, such defective blocks are replaced by normal blocks in the spare area and the data to be recorded in the defective block are recorded in an assigned spare area. To achieve the replacement, a physical sector number (PSN) assigned to a defective block remains, while a logical sector number (LSN) is moved to the replacement block along with the data to be recorded. Linear replacement is effective for non real-time processing of data. For convenience, a data which does not require real time processing is hereinafter called a personal computer (PC)-data.
If a replacement block listed in the SDL is found to be defective, a direct pointer method is applied to the SDL listing. According to the direct pointer method, the defective replacement block is replaced with a new replacement block and the SDL entry of the defective replacement block is modified into a sector number of the first sector of the new replacement block.
FIG. 4A shows a procedure to manage a defective block found while writing or reading data into or from the user area. FIGS. 4B˜4D show embodiments of SDL entries generated according to the linear replacement algorithm. Each SDL entry has, in order, a FRM, a sector number of the first sector of the defective block, and a sector number of the first sector of the replacement block.
For example, if the SDL entry is (1, blkA, 0) as shown in FIG. 4B, a defective block has been newly found during the reproduction and is listed in the SDL. This entry indicates that a defect occurs in block blkA and that there is no replacement block. The SDL entry is used to prevent data from being written into the defective block in the next recording. Thus, during the next recording, the defective block blkA is assigned a replacement block according to the linear replacement.
An SDL entry of (0, blkA, blkE), shown in FIG. 4C, indicates that the assigned replacement block blkE has no defect and data to be written into the defective block blkA in the user area is written into the replacement block blkE in the spare area. An SDL entry of (1, blkA, blkE) shown in FIG. 4D, indicates that a defect occurs in the replacement block blkE of the spare area which replaced the defective block blkA of the user area. In such case, a new replacement block is assigned according to the direct pointer method.
FIG. 5 is a partial diagram of an optical disc recording/playback (R/P) device relating to the recording operation. The optical disc (R/P) device includes an optical pickup to write data into and playback data from the optical disc; a servo unit controlling the optical pickup to maintain a certain distance between an object lens of the optical pickup and the optical disc, and to maintain a constant track; a data processor either processing and transferring the input data to the optical pickup, or receiving and processing the data reproduced through the optical pickup; an interface transmitting and receiving data to and from an external host; and a micro processor controlling the components. The interface of the optical disc R/P apparatus is coupled to a host such as a PC, and communicates commands and data with the host.
If there is data to be recorded in an optical disc R/P apparatus, the host sends a recording command to the optical disc R/P apparatus. The recording command comprises a logical block address (LBA) designating a recording location and a transfer length indicating a size of the data. Subsequently, the host sends the data to be recorded to the optical disc R/P apparatus. Once the data to be written onto an optical disc is received, the optical disc R/P apparatus writes the data starting from the designated LBA. At this time, the optical disc R/P apparatus does not write the data into areas having by referring to the PDL and SDL which indicate defects of the optical disc.
Referring back to FIG. 4A, the optical disc R/P apparatus skips physical sectors listed in the PDL and replaces the physical blocks listed in the SDL, within the area between A and B, with assigned replacement blocks in the spare area during the recording. If a defective block not listed in the SDL or a block prone to an error is found during the recording or playback, the optical disc R/P apparatus considers such blocks as defective blocks. As a result, optical disc R/P apparatus searches for a replacement block in the spare area to rewrite the data corresponding to the defective block and lists the first sector's number of the defective block and the first sector's number of the replacement block at the SDL entry.
To perform the linear replacement, namely to write the data into the assigned replacement block in the spare area when finding a defective block (listed or not listed in the SDL), the optical disc R/P apparatus must move the optical pickup from the user area to the spare area and then back to the user area. Because moving the optical pickup may take time, a linear replacement interferes a real time recording.
Thus, defect area management methods for real time recording, such as audio visual apparatus, have been extensively discussed. One method is to use a skipping algorithm where a defective block is skipped and data is written into the next normal block, similarly to the slipping replacement algorithm. If this algorithm is employed, the optical pickup does not need to be moved to the spare area whenever a defective block is found, such that the time needed for moving the optical pickup can be reduced and the interference with the real time recording can be removed.
For example, if the PC-data which does not require real time processing, as shown in FIG. 4A, is received when the SDL is used, the linear replacement algorithm is executed upon finding defective blocks blkA and blkB. If the received data requires real time, as shown in the area between B and C of FIG. 4A, the skipping algorithm is used upon finding defective block blkC. Namely, the linear replacement is not performed. For linear replacement, the PSN of the defective block is maintained as is and the LSN of the defective block is moved to the replacement block. For the skipping algorithm, both the LSN and PSN of the defective block blkC are maintained as they are.
Accordingly, when the host reads the data recorded according to the skipping algorithm, the microprocessor transmits all data including data of defective blocks through the interface. However, the host cannot identify the data of the skipped defective block since it does not have information regarding the skipped defective blocks, resulting in an incorrect playback of the data. Therefore, the microprocessor of the optical disc R/P apparatus must instruct the optical pickup not to read the data of defective blocks among the data playback from the optical disc and transmitted to the host. Here, the information regarding the defective blocks, as shown in FIGS. 4B˜4D, remains in the SDL and the microcomputer may transmit the information to the host, on request.
The SDL is information on defective blocks with respect to the linear replacement algorithm. However, the microprocessor cannot discriminate information recorded with respect to linear replacement from information recorded with respect to skipping algorithm not performing the linear replacement. Consequently, if skipping algorithm has been used, the microprocessor may transmit incorrect information to the host. Likewise, the host cannot identify the data of skipped defective blocks, resulting in an erroneous playback of data.
Moreover, because of the size of the spare may not be sufficient, the spare area may become full while the DMA has redundant areas for listing defective blocks at the PDL or SDL entries. If the spare area is full, a spare full flag in the DMA is set. The spare area may become full prior to the DMA when the initial allocation of spare area is insufficient or when the available spare area is quickly reduced due to defects, particularly burst defects occurring in the spare area. Because it is desirable to increase the recording capacity of the optical disc, a method of further reducing the size of the spare area has been considered. In such case, however, there is a higher possibility that the spare area will become full prior to the DMA.
Consequently, if the optical disc R/P apparatus finds a defective block that is not listed in the SDL or is listed in the SDL but requires a new replacement block as shown in FIGS. 4B˜4D while recording or playing back data, it checks the spare full flag of the DMA. If the spare full flag is in a reset state which indicates that available spare areas remain, the apparatus records the data of the defective block in a replacement block in the spare area and lists a new SDL entry or modifies the existing SDL entry. On the other hand, if the spare full flag is in a set state, which indicates that the spare area is full, a linear replacement cannot be executed even if the DMA has redundant area. If the linear replacement cannot be executed when necessary, the management of defective area cannot be maintained. As a result, the disc cannot be used.